Subsurface gun firing apparatus



2 Sheets-Sheet l INVENToR. M. RAGA/v,

T. M. RAGAN SUBSURFACE GUN FIRING APPARATUS May l0, 1955 Original FiledJan. 12 1948 May 10, 1955 T. M. RAGAN 2,707,999

sUBsURFAcE GUN FIRING APPARATUS original Filed Jan. 12, 1948 2sheets-sneu 2 j f Q i Vw 9g f Q/15 A 1 i f H y [l Q40! W a4- kw E f gg/3:? v; f 75' -a W f5 7 4. 75 75a iig 732 74 @9 7 M5 ,ummm ,rllj/ .ft.'60 M MH', A g

AHunnlm///f t iii kaf 6'" l 4? *lk/:70 INVENTOR;

` I Z50/14,45 M. RAe/1N,

SUBSURFACE GUN FIRING APPARATUS Thomas M. Ragan, Downey, Calif.,assignor to Baker f(lil Tools, Inc., Vernon, Calif., a corporation ofCaliorma The present invention relates to well devices, and moreparticularly to subsurface devices adapted to perform desirableoperations in oil, gas and similar well bores.

This application is a division of the application of Reuben C. Baker,Thomas M. Ragan, John R. Baker and Martin B. Conrad, Serial No. 1,845,tiled January 12, 1948, for Gas Operated Well Apparatus, now Patent No.2,640,547.

An object of the present invention is to provide an improved apparatusfor initiating combustion of a charge in a well device that is tooperate the device. r

Another object of the invention is to provide improved apparatus forfiring an explosive in subsurface well apparatus.

A further object of the invention is to provide an improved subsurfacewell apparatus embodying a tiring pin which is positively held initiallyin ineffective position, and which is mechanically releasable for thepurpose of firing a cartridge or other explosive disposed in the wellbore.

Yet another object of the invention is to provide an improved releasablelatch arrangement in a subsurface well tool for initially holding atiring pin, or the like, in an ineffective position.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of a formin which it may be embodied. This form is shown in the drawingsaccompanying and forming part of the present specication. lt will now bedescribed in detail, for the purpose oi illustrating the generalprinciples of the invention; but it is to be understood that suchdetailed description is not to be taken in a limiting sense, since thescope oi the invention is best deiined by the appended claims.

Referring to the drawings:

Figures l, la and lb together constitute a longitudinal section throughan apparatus, with the parts in position for moving the apparatuslengthwise through a well casing, Fig. lb constituting a lowercontinuation of Fig. la, and Fig. la constituting a lower continuationoi Fig. l;

Fig. 2 is a longitudinal section disclosing the tiring pin portion ofthe apparatus in another operative position; l

Fig. 3 is an enlarged longitudinal section through the firing pinportion of the device prior to firing of an explosive cartridge, or thelike;

Fig. 4 is a view similar to Fig. 3 after the firing pin has tired thedevice.

The invention is disclosed in the drawings as applied to a well packerA, which is to be anchored at a desired location in a well casing Bdisposed within a bore hole. The packer is anchored in packed-oitcondition against the well casing through use of a setting tool Cconnected to it, which is attached to the lower end of a running-instring, such as a wire line D, extending to the top of the well bore. Ifdesired, a sinker bar or jarring device E ZQQQ Patented May l0, 1955 maybe interposed between the wire line D and setting tool C.

The well packer A may assume any desired form. The packer disclosed inthe drawings includes a tubular body 1t) whose central passage 11 may beclosed by a plug 12. A guide 13 is secured to the lower end of the body16 to prevent hanging up of the tool in the casing joints or couplingspaces during its lowering through the well casing B.

The well packer can be anchored against downward movement in the wellcasing by a plurality of lower segmental slips 14, whose lower endengages the guide 13 and a lower abutment or ange 15' on the body. Theinner surfaces 16 of these slips are tapered in a downward and inwarddirection for slidable engagement with a corresponding externallytapered surface 17 on a frustoconical expander 18 slidable on the body.This expander is connected to the lower end of a packing sleeve 19, ofrubber or similar material, disposed around the body 10, the upper endof this packing sleeve being connected to an upper expander 2() havingan upward and inwardly inclined externally tapered surface 21 engageablewith corresponding tapered surfaces 22 on a plurality of upper segmentalslips 23.

Initially, the slips 14, 23 and packing element 19 are retained inretracted positions with respect to the packer body 1li. Shear screws24, 25, or other suitable frangible connecting elements, secure theupper and lower conical expanders 2i), 1S to the body, with theintervening packing sleeve 19 held in retracted position. The upper andlower slips 23, 14 are also held in retracted positions by shear screws26, 27 attaching them to their associated upper and lower expandets 20,13.

The shear screws 26, attaching the upper slips 23 to the upper expander20, have a combined shearing strength which is substantially less thanthe shear value of the screws 24 holding the upper expander to the body10. These latter screws have alesser shear value than the screws 25, 27securing the lower expander 18 to the body and the lower slips 14 to thelower expander. These relative shear values are selected to securedetachment first of the upper slips 23 from the upper expander 2.0, andmovement of the upper slips downwardly along the upper expander andradially outward into anchoring engagement with the casing wall.Subsequent upward strain or pull on the packer body 10 then shears thescrews 24 expansion into iirm sealing engagement with the wall of thecasing. Thereafter, an increase in the upward pull or force on thepacker body 10 substantially simultaneously shears the screws 25, 27holding the lower expander 18 to the body and the lower slips 14 to thelower exv pander, to cause the lower ilange 15 and guide 13 on the bodyto shift the lower slips 14 upwardly along the lower expander andradially outward into anchoring engagement with the wall of the casingB. A split, contractile ring 2S may be disposed in the upper expanderfor engagement with one of several circular ratchet teeth 29 formed onthe exterior of the body lil, to lock the latter against downwardmovement. The set and anchored position of the well packer A isillustrated in the aforesaid parent application, Serial No. 1,845.

lt is evident from the foregoing description that the full setting ofthe packer A in the well casing B has occurred as a result of a definitesequence of steps. These are the outward movement of the upper slips 23to casing engaging position, the expansion of the packing ele-w ment 19against the casing, and the subsequent engagement of the lower slips 14with the casing. A definite time interval should be provided betweenthese main operational steps to insure proper setting of the packer inthe well casing. In the present instance, it is dcsired to provide forsuch operational sequence by the use of a force developed by products ofcombustion within the setting tool C connected to the well packer A, inorder to enable the well packer to be run in the casing on a wire lineD.

As disclosed in the drawings, gas pressure is developed within acylinder 30 consisting of a generally cylindrical sleeve 31, an upperhead 32 threaded into the sleeve, and a lower head 33 threaded into thesleeve. A piston 40 is slidably mounted in the cylinder 30. This pistonhas one or more ring grooves 41 in its periphery for the accommodationof seal rings 42 to prevent leakage between the piston and cylinder. Asdisclosed, these rings 42 may consist of rubber of round cross-sectionto guard against leakage in either direction. The upper end of a pistonrod 43 is threadedly connected to the piston 40, the rod extendingdownwardly through the lower cylinder head 33 to a point therebelow,where an anvil or cross-piece 44 is mounted within a transverse slot 45in the rod. Leakage between the rod 43 and lower cylinder head 33 isprevented by suitable rod packing in the form of one or more roundrubber or rubberlike seals 46 engaging the periphery of the rod anddisposed within suitable ring grooves 47 in the head.

It is desired to transfer the downward movement or force of the piston4% and piston rod 43 to the upper slips 23 of the packer, and therelative upper movement of the cylinder 30 to the packer body 10 inorder to obtain the desired anchoring of the packer in the well casing.To accomplish this purpose, a tubular actuating mandrel 43 is threadedlyconnected to the lower end of the lower cylinder head 33. The lower end50 of this mandrel is secured to a sleeve 49, threaded into the upperend of the body 10, through the agency of a frangible pin 51. Asspecifically disclosed, the lower end l) of the mandrel is of reduceddiameter and is piloted within the sleeve 49, the pin 51 extendingtransversely through the sleeve 49 and piloted mandrel portion 50.

The piston rod 43 is movable downwardly within the bore 52 of theactuating mandrel 48, the cross-piece 44 projecting in oppositedirections from the rod through diametrically opposed longitudinallyextending slots 53 formed through the mandrel wall. The cross-piece 42also extends into opposed slots 55 formed through a setting ring orsleeve 56 slidably mounted on the actuating mandrel 48, to form aconnection between the piston rod 43 and the setting ring 56. A settingsleeve or skirt 57 is adjustably threaded on the setting ring, thisskirt depending from the ring and being slidable along a ange or head 58threaded on the lower end of the actuating mandrel 43. Leakage aroundthe head is prevented by a suitable seal ring 58a mounted on it engagingthe sleeve 57. This sleeve 57 extends beyond the head 58 and may berotated or threaded on the setting ring to engage its lower end 59 withthe tops of the upper slips 23.

A uid or gaseous force is developed within the cylinder 30 above thepiston 40, this force moving the piston and piston rod 43 downwardly andthe cylinder 30 relatively upwardly. The downward movement of the rod 43is transmitted to the setting sleeve or skirt 57 through the anvil 44and setting ring 56, while the upward movement of the cylinder 30 istransmitted to the packer body through the actuating mandrel 48,frangible pin 51 and sleeve 49. Accordingly, it is apparent that thedevelopment of sufficient pressure in the cylinder 30 will eventuallyshear the screws 26 holding the upper slips 23 to the expander 20, andmove the slips outwardly against the casing B, whereupon the cylinder 30will move upwardly to pull the body 1') in the same direction to expandthe packing sleeve 19 against the casing B, and then the lower slips 14against the casing.

ln order to obtain the desired operational sequence, a combustible fuel,fusee or railway flare is contained within the upper end of the cylinder30. This fuel has a slow burning rate and may require several secondsafter its ignition to develop sufficient gaseous pressure for fullysetting the well packer A, and for applying suicient upward force on thecylinder to shear the frangble pin 51 attaching the setting tool C tothe well packer, for the purpose of removing the setting tool from thewell bore. One form of fuel actually used in the cylinder requires fromeight to twelve seconds to develop gradually a sufficiently highpressure to fully set the well packer A and shear the pin Si, assumingthat about 25,000 lbs. total force is required to disrupt the pin. Thisis to be distinguished from the use of an explosive, whose full pressureand expansion force is developed and applied instantaneously.

The fusee 60 is ignited by a blank cartridge 64, which is containedwithin a gun barrel inserted Within the upper end of the cylinder head32, Leakage between the barrel 65 and head is prevented by a suitableside seal 66 on the barrel engaging the wall of the head. The barrel isthreaded into a gun body 67 which is threadedly secured to the upper endof the cylinder head 32. This body 67 also contains a breechblock or cap63 threaded onto the upper end of the barrel 65 and having an inwardlydirected ange 69 tirmly engaging a thin metallic disc 70 bearing againstthe cap 71 of the cartridge. In effect, the breechblock 63 clamps thedisc 7) and cartridge cap 71 to the gun barrel 65, leakage in an upwarddirection from the barrel being prevented by a suitable gasket 72 in thebarrel bearing against the thin disc 70.

The cartridge 64 is tired by a pin 73 whose tapered end 73a can enter atapered hole 74 in the brecchblock to strike and indent the disc 79, andthereby fire the cartridge. The ilarne from the cartridge ignites theupper end of the fusee 60 and initiates its combustion, which thenbecomes self-sustaining.

The tapered lower end 73a of the tiring pin 73 extends downwardly from aflange or spring seat 75 integral with the tiring pin shaft 76, all ofthese elements being disposed within the gun body 67. A compressedhelical spring 77 is disposed between the seat 75 and the upper end ofthe central bore 78 through the body, this spring exerting suicientforce to shift the pin 73 downwardly and strike its end 73a against thethin disc 70, in order to tire the cartridge 64.

The shaft 76 of the pin extends upwardly through an elongate transverseslot 79 within the body 67, its upper end being formed with a pair ofwings or hooks Si) adapted to be engaged by inwardly directed latchngers 71 on the lower ends of latch levers 82 disposed in the body slot79 and pivotally mounted on pins 83 supported in the body. The upperarms 84 of the levers are urged in an outward direction, to maintain thelatch fingers S1 engaged under the tiring pin hooks 80, by an expansiblespring 85, whose opposite ends are received within recesses 86 in thearms 84. So long as the spring S5 holds the upper lever arms 84outwardly and the latch tngers 81 under the tiring pin hooks 80, thefiring pin 73 is maintained in elevated position above the disc 70 andcartridge 71, holding the tiring spring 78 in a highly compressedcondition.

The latch lever arms 84 are movable inwardly toward each other, to swingtheir fingers 81 outwardly from engagement with the tiring pin 73,allowing the tiring spring 78 to move the point 73.11 of the pindownwardly and strike it against the disc 79. In the event that thepoint pierces the disc, rather than merely indents it, the downwardmovement of the pin is limited by engagement of a transverse rod 87extending through the pin '73 with a stop pin 88 secured to the gun body67 and extending into or across its slot 79. As a precautionary measure,a hole 89 is provided through the gun body 67 into its slot 79 for theinsertion of a safety pin (not shown), which holds the ring pin 73 inelevated position against the force of its spring 78 during assembly ofthe mechanism. Should the latch levers 82 become released inadvertentlyduring assembly, the tiring pin 73 could move downwardly only to aslight extent as determined by engagement of the rod 87 with the safetypin in the hole S9. Of course, after the tool has been completelyassembled, and prior to its lowering in the well bore, the safety pin isremoved from the hole 89 to permit unrestricted downward movement of theliring pin 73 when released.

The upper end of the gun body 67 is threaded into a sinker bar orjarring device E to provide suicient weight for forcing the entireapparatus through the well uid during its descent in the casing B. Theupper end of the jarring device or sinker bar is secured to a wire linesocket 90 having an enlarged bore 91 for the reception of the unraveledlower end of the wire line D. As is well L known, the wire line may befirmly secured in the socket by filling the bore 91 of the latter withBabbitt metal 92, or any other suitable material.

As disclosed in the drawings, the cartridge 64 is lred by mechanicalinstrumentalities. For the purpose of moving the latch lever arms 84inwardly, a friction drag device 99 may be employed. This deviceincludes upper and lower collars 100, 101 slidable along the wire linesocket 90, jarring mechanism E and gun body 67. The upper and lower endsof outwardly bowed drag springs 102 are suitably secured to thesecollars, as by the use of encompassing rings 103 and screws 104. Thesprings 102 frictionally engage the wall of the well casing B, whichtends to resist its movement therewithin. Nevertheless, the drag device99 is forced through the well casing, during lowering movement of theapparatus therewithin, by engagement of the upper collar 100 with ashoulder 105 on the wire line socket 90. Upward movement ofthe wireline, after the desired packer setting location has been reached in thewell bore, moves the entire apparatus, with the exception of the dragdevice 99, upwardly within the casing, pulling the latch levers 82within the lower drag collar 1G31 (see Fig. 2), and causing the latterto shift the latch lever arms 84 inwardly and release the fingers 81from the tiring pin 73, whereupon the spring 7S is free to strike thepin end 73a against the disc 7G and lire the cartridge 64.

Actually, the entire apparatus is lowered in the well casing to a pointbelow the desired setting location of the bridge plug in the casing B.This distance below the desired location is the relative distance thatthe lower drag collar 101 must travel along the jarring device E andbody 67 to release the latch levers S2 from the firing pin 73.Accordingly, subsequent elevation of the Wire line D by this distancewill pull the levers 32 within the drag collar 101, to release the pin73, fire the cartridge 64 and ignite the fusee 60. Assurance is thusobtained of setting the packer A at the intended point in the wellcasing B.

Full operation of the apparatus in the well casing will now bedescribed. The equipment is assembled on the lower end of the wire orother iiexible line D, with the parts in the relative positions shown inFigs, l, 1a, lb. The tool is lowered through the well casing B to apoint a little below the location at which the packer A is to beanchored to the casing. The wire line D is then pulled upwardly, whichmoves the drag device 99 relatively in a downward direction until itslower collar 101 is disposed over and against the upper latch lever arms84, fo r cing them inwardly and releasing the latch fingers 81 from thetiring pin 73. The spring 78 then shifts the tiring pin '73 rapidlydownward, to engage its point '73a with the thin disc 70, striking thedisc and cartridge head 71 with sulicient force to fire the cartridge 64(see Figs. 2 vand 4). The flame emanating from the cartridge ignites thecharge of black powder, or other equivalent igniting substance, at theupper end of the combustible charge or fusee 60, which begins burningaway in a downward direction.

The gases or products of combustion gradually build up pressure in thetiring chamber 61 in the head 32 and cylinder 30, urging the piston 40downwardly and the cylinder 30 upwardly. The force of the piston 40 istransmitted through the rod 43, cross-piece 44 and setting ring 56 tothe sleeve 57, which bears against the upper slips 23. When sutlicientpressure has been developed in the cylinder to overcome the shearstrength of the screws 26, and also the hydrostatic head of iluid actingupwardly on the piston rod 43, the slips 23 are released from theexpander 20 and are pushed downwardly along the latter into outwardengagement with the casing B.

As the combustible charge 60 continues to burn, the gas pressure withinthe cylinder 30 increases to a further extent. Since the upper slips 23are wedged against the casing B, the piston cannot move downwardly toany further appreciable extent. Instead, the cylinder 30, actuatingmandrel 4i8, sleeve 49 and packer body 10 are urged in an upwarddirection. When the pressure or force in the cylinder has increasedsuiiciently to overcome the shear strength of the screws 24 holding theupper expander 20 to the body, such screws are disrupted and the packerbody 10 is moved upwardly within the upper expander 20 to compress thepacking sleeve 19 between the upper and lower expanders 20, 18 and lorceit into rm sealing engagement with the casing wall.

As the cylinder gas pressure increases further, as a result of thecontinued combustion of the charge 60, the shear values of the screws25, Z7 attaching the lower expander 18 to the body 10 and the lowerslips 14 to the lower expander are exceeded, and these shear screws' aredisrupted, allowing the cylinder 30 to move upwardly and carry the body10 and lower slips 14 in an upward direction, to shift the latterradially outward into engagementl with the casing B.

The pressure in the cylinder continues to increase, as combustion of thecharge proceeds, and all of the packer elements are engaged more firmlywith the casing B. When the pressure exceeds the shear strength of thepin 51 securing the lower end 50 of the actuating mandrel 48 to thesleeve 49, this pin is sheared to release automatically the setting toolC from the well packer A. All of the mechanism, with the exception ofthe packer may now be removed from the well casing B.

The inventor claims:

l. In well apparatus: a well device adapted to be operated in a wellbore; fluid actuated means for operating said well device, comprisingcylinder and piston means; a slow burning combustible product in saidcylinder and piston means; an explosive in said cylinder and pistonmeans for initiating combustion of said product; a tiring pin engageablewith said explosive to eiect its discharge; spring means engaging saidtiring pin to propel said tiring pin toward said explosive; latch meansengaging said firing pin to hold it against the torce of said springmeans out of engagement from said explosive; and means for releasingsaid latch means from said firing pin.

2. In well apparatus: a well device adapted to be lowered in a wellbore; means for operating said device, including an explosive; means fortiring said explosive, comprising a gun body, a ring pin slidable onsaid body, spring means engaging said body and pin for urging said pintowards said explosive, latch means on said body engageable with saidpin to hold it against the force ofsaid spring means; and meansrelatively movable along the ex- 7 said pin towards said explosive,latch means on said body cngageable with said pin to hold it against theforce of said spring; and a drag device relatively movable along saidbody, in response to longitudinal movement of said wire line, intoengagement with said latch means to release said latch means from saidpin.

4. In well apparatus: a wcll device adapted to be lowered in a wellbore; means for operating said device, includingr an explosive; meansfor tiring said explosive, comprising a gun body, a tiring pin slidableon said body, a spring engaging said body and pin for urging said pintowards said explosive; opposed latch levers pivotally mounted on saidbody and engageable with said pin to hold it against the force of saidspring; and means relatively movable along said body into engagementwith said latch levers to release them from said pin.

5. In well apparatus: a Well device adapted to be opcrated in a wellbore; means for operating said well device, including an explosive; amember operatively connected to said operating means; means for tiringsaid explosive; a latch initially engaging said tiring means to preventits operation; and a drag device engageable with the wall of the wellbore and slidable on said member into engagement with said latch torelease said latch from said firing means to permit said tiring means tolire said explosive.

6. ln well apparatus: a well device adapted to be lowered in a wellbore; means for operating said device, including an explosive; means fortiring said explosive, comprising a gun body, a tiring pin slidable onsaid body, a spring engaging said body and pin for urging said pintoward and against said explosive, latch means on said body engageablewith said pin to hold it against the force of said spring, and meansholding said latch means in engagement with said pin.

7. In well apparatus: a well device adapted to be lowered in a wellbore; means for operating said device, including an explosive; means fortiring said explosive, comprising a gun body, a tiring pin slidable onsaid body, spring means engaging said body and pin for urging said pintoward said explosive, latch means on said body engageable with said pinto hold it against the force of said spring means, means holding saidlatch means in engagement with said pin; and means relatively movablealong the exterior of said body into engagement with said latch means torelease said latch means from said pin.

8. In well apparatus: a well device to be lowered in a well bore; meansfor operating said device, including a body, a member slidable on saidbody and occupying an initial position thereon, means engaging said bodyand member for urging said member relative to said body from saidinitial position, latch means on said body engagcable with said memberfor holding said member in said initial position against the force ofsaid urging means; and means relatively movable along the exterior ofsaid body into engagement with said latch means to release said latchmeans from said member to allow said urging means to shift said memberfrom said initial position relative to said body.

9. In well apparatus: a well device to be lowered in a well bore; meansfor operating said device, including a body, an explosive in said body,a member slidable on said body into engagement with said explosive toetect its discharge, means engaging said body and member for urging saidmember relative to said body into engagement with said explosive, latchmeans on said body engageable with said member for holding said memberagainst the force of said urging means out of engagement from saidexplosive, and means holding said latch means in engagement with saidmember.

10. In well apparatus: a well device to be lowered in a well bore; meansfor operating said device, including a body, a member slidable on saidbody, a spring engaging said body and member for urging said memberrelative to said body, opposed latch levers pivotally mounted on said 8body and engageable with said member to hold it against the force ofsaid spring, and means holding said latch means in engagement with saidmember.

ll. In well apparatus: a well device to be lowered in a well bore; meansfor operating said device, including a body, member slidable on saidbody, a spring engaging said body and member for urging said memberrelative to said body, opposed latch levers pivotally mounted on saidbody and engageable with said member to hold it against the force ofsaid spring, means holding said latch means in engagement with saidmember; and means relatively movable along said body into engagementwith said latch levers to release them from said member.

l2. In well apparatus: a well device adapted to be lowered in a wellbore; means for operating said device, including an explosive; means fortiring said explosive, comprising a gun body, a firing pin slidable onsaid body and having a plurality of hooks thereon, a spring engagingsaid body and pin for urging said pin toward said explosive; latchlevers pivotally mounted on said body and having lingers engageable withsaid hooks to hold said pin against the force of said spring; and meansrelatively movable along said body into engagement with said latchlevers to release said lingers from said pin.

i3. In well apparatus: a well device to be lowered in a well bore; meansfor operating said device, including a body, a member slidable on saidbody and having hooks thereon, means engaging said body and member forurging said member relative to said body, latch elements mounted on saidbody and having fingers engageable with said hooks to hold said memberagainst the force of said urging means, and means holding said latchfingers in engagement with said hooks.

14. In well apparatus: a well device to be lowered in a well bore; meansfor operating said device, including a body, a member slidable on saidbody and having hooks thereon, means engaging said body and member forurging said member relative to said body, latch elements mounted on saidbody and having lingers engageable with said hooks to hold said memberagainst the force of said urging means, means holding said latch fingersin engagement with said hooks; and a drag device slidable on said bodyinto engagement with said latch elements to release said fingers fromsaid hooks'.

l5. In well apparatus: a well device adapted to be operated in a wellbore; means for operating said device, including a gun barrel; anexplosive in said barrel; a cap secured to said barrel and having anopening therein; a thin disc clamped between said cap and barrel toclose said gun barrel, said disc extending across said opening; and atiring pin movable into said opening into engagement with said disc tore said explosive.

i6. In well apparatus: a well device adapted to be operated in a wellbore; means for operating said device, including a gun barrel; anexplosive in said barrel; a cap secured to said barrel and having anopening therein; a thin disc clamped between said cap and barrel toclose said gun barrel, said disc extending across said opening; a gasketclamped between said disc and barrel; and a tiring pin movable into saidopening into engagement with said disc to fire said explosive.

17. In well apparatus: a well device adapted to be lowered in a wellbore; means for operating said device, including a body, a memberslidable on said body, a spring engaging said body and member for urgingsaid member relative to said body, a latch lever pivotally mounted onsaid body and engageable with said member to hold it against the forceof said spring, and means holding said latch lever in engagement withsaid member.

References Cited in the tile of this patent UNITED STATES PATENTS2,100,807 Kinley Nov. 30, 1937 2,327,362 McDonald et al Aug. 24, 19432,373,006 Baker Apr. 3, 1945

